1. Field of the Invention
The present invention relates to a method and compositions therefor for rendering structures subject to aquatic environments resistant to fouling by aquatic organisms such as barnacles, algae, sea moss, slime, etc. It particularly relates to the control of such organisms through the use of novel antifouling agents.
2. Description of the Prior Art
As used herein, the term "structure subject to aquatic environments" refers broadly to any object which is in contact with an aqueous environment. By way of example, but not of limitation, such structures include all forms of watercraft, including both the moving and static varieties; underwater static structures such as wharfs, piers, pilings, bridge substructures, etc.; underwater machinery such as heat exchangers, water inlet and outlet pipes, pumps, etc.; and such objects as ropes, fishnets, etc. In short, any object which is in contact with a water environment, and upon which the growth of fouling organisms is undesirable may be efficaciously protected through the use of the method and compositions of the instant invention. Currently, in coastal areas large quantities of sea water are utilized by power plants, petrochemical plants, etc. as industrial cooling water. In these installations, the attachment and growth of Hydrozoa, Hydroides norvegica, Ostrea, Mytilus edulis, Balanus amphitrite hawaiensis, Bryozoa, Ulva, Enteromorpha, Ectocarpus, Ascidiacea, on the waterway heat exchangers and the main and auxiliary water pipes adapted for intake and disposal of waste cooling water result in such undesirable consequences such as the reduction of sea water intake, reduction of cooling efficiency, and the fouling of water pipes. Similarly, the deposit and growth of these fouling organisms on the bottoms and sides of ships and other watercraft causes a reduction in cruising speed, increased fuel costs, and an accelerated corrosion of hull materials. The above-mentioned fouling organisms also attach themselves to fishnets, ropes, etc., regardless of whether they are manufactured of synthetic or natural fiber, gradually plugging the meshes of the nets or increasing the surface area of the ropes, increasing their wave resistance with an attendant debilitive effect on net deployment. The growth of these organisms on fishnets used in fish nurseries, such as yellowtail nurseries, has a particularly deleterious effect, causing a reduction in the supply of nutrients available to the fish, or a sagging or breaking of fishnets due to their increased weight, both of which result in a reduction of fish yield. The underwater structures, rigs, machinery, etc. are also subject to biological degradation of their materials due to the deposit and growth of the above fouling organisms, or are subject to handling inconveniences. Heretofore, chlorine, sodium hypochloride, formalin, etc. have been employed for the prevention of the attachment and growth of such fouling organisms in aquatic structures. However, these substances have been less than satisfactory in that they are not only inadequate in activity against these fouling organisms, but tend to cause pollution and corrosion of equipment. Furthermore, marine paints and underwater antifouling paints containing compounds of tin, mercury, copper, zinc, arsenic, or other metals have been employed by the prior art in an effort to combat the attachment and growth of fouling organisms on ships and other underwater structures. However, these metallic compounds have proved to be unsatisfactory in that they tend to corrode ship-hull materials or to be deactivated by reactions with the hydrogen sulfide present in harbor and port water. It has also been proposed in Japanese Patent Publication No. 34448/1976, Japanese Patent Application Laid-Open No. 118830/1976; and Japanese Patent Application Laid-Open No. 132223/1976 to employ certain geraniol compounds as antifouling agents. However, even these compounds exhibit a still less than desirable activity against the above-mentioned fouling organisms.
Therefore, in the watercraft, harbor, power, chemical, and fish-nursing industries, research has continued for compounds which exhibit a high selective activity against the aforementioned aquatic fouling organisms, which exhibit a low toxicity to human beings and other animals, a low toxicity to fish and edible shell-fish, and which are easy to handle, and have a long duration of activity.